Start by creating a sample design that includes your close image in the top right corner. Once you have this ready, utilize jquery to display it when hovering over:
$('#Image1').on('mouseenter', function() { $('#closeImg').show(); });
You can position the close image like this:
<div class="img-container">
<div class="close-img"><img src="..." /></div>
<img src="..." />
</div>
CSS:
.img-container { position: relative; }
.close-img { position: absolute; top: 0; right: 0; z-index: 99; }
--- Update: If you desire some special effects, follow the jquery method above. Alternatively, you can use the pure CSS approach (
.img-container:hover .close-img { display: block }
) suggested by others for a different solution.